Assessing the spatial pattern of capacity and demand for coastal protection ecosystem services in mainland China

Coastlines are increasingly threatened by natural hazards such as intensifying storms, flooding, and erosion. The safety of lives and property in coastal zones can only be ensured when the biophysical capacity for coastal protection services adequately meets demand. Yet existing capacity-demand models often fail to account for the combined impacts of marine and terrestrial hazards (e.g. extreme rainfall coinciding with storm surges) and the mitigating effects of human critical infrastructure (e.g. dikes). To address this gap, we analyzed 228 county-level coastal assessment units along the Chinese mainland. First, we measured the biophysical capacity of coastal protection services using five indicators related to natural ecosystem properties. Next, we evaluated demand for coastal protection services by integrating six natural hazard indicators, four human exposure indicators, and four social adaptive capacity indicators into a risk reduction model. Finally, we identified nine distinct types of capacity-demand relationships across space (High-Low, High-Medium, High-High, Medium-Low, Medium-Medium, Medium-High, Low-Low, Low-Medium, and Low-High). Seventy-seven counties exhibited relatively low capacity and relatively high demand, located mostly in Guangdong and Jiangsu provinces. Furthermore, we found that many economically underdeveloped counties showed capacity-demand mismatches (e.g. the coastal counties of Hainan Province), perhaps because local infrastructure development has not kept pace with overall economic growth. This study provides a comprehensive framework for identifying spatial patterns of coastal protection services capacity-demand mismatches, thereby informing decision-making to enhance disaster resilience in China's coastal zones.